Japan's benchmark Nikkei 225 Stock Average fell below 11,000 Friday, hitting its lowest mark since May 2005, and the Topix index dropped more than 2 per cent after overnight plunges on Wall Street, reported dpa.
The Nikkei plunged to 10,938.14, down 216.62 points, or 1.94 per cent.
The broader Topix index of all first-section issues also lost 29 points, or 2.69 per cent, to 1,047.97.
Tokyo players sold a wide range of issues as they grew increasingly worried over the course of the US and Japanese economies.
For the week, the Nikkei tumbled 8.03 per cent, and the Topix declined 8.7 per cent.
To ease disruptions in financial markets, Japan's central bank injected 800 billion yen (7.58 billion dollars) into the money markets. It was the 13th-consecutive business day it had made such an injection.
The total amount of liquidity now infused into the economy by the Bank of Japan comes to 24.3 trillion yen since the US investment bank Lehman Brothers Holdings Inc filed for bankruptcy on September 15.
On currency markets at midday (0300 GMT), the dollar was quoted at 105.05-10 yen, down from Thursday's 5 pm quote of 105.32-34 yen.
The euro was quoted at 1.3830-35 dollars, down from Thursday's 5 pm quote of 1.3880-82 dollars, and at 145.30-35 yen, down from 146.19-23 yen.